Internal Processes Flashcards
Divergent boundary
1) Magma rises between two plates –> going away from each other
2) EITHER midocean ridge OR continental rift
Convergent boundary
1) plates colliding, destructive boundaries
2) lead to orogenesis (mountain building)
3) 3 types: oceanic-continental, oceanic-oceanic, continental-continental
Oceanic-continental convergence
1) Oceanic plate goes into asthenosphere of continental
2) Features: creates oceanic trench + volcanic mountains on continental crust
Oceanic-Oceanic Convergence
1) More dense oceanic crust subducts
2) Water involved –> cool magma, produces felsic
3) Key Features = oceanic trench, volcanic arc
Continental Continental Convergence
1) No subduction because continental crust too buoyant
2) creates huge mountain ranges like himalayas
Transform boundaries
1) plates slide laterally –> no new crust created or old crust destroyed
2) found in midocean ridges + in California
Two additions to plate tectonic theory
1) hot spots
2) accreted terranes
Hot Spots
1) Explains the formation of volcanic islands and seamount chains away from tectonic plate boundaries.
2) A hotspot is a stationary mantle plume that creates volcanic activity as tectonic plates move over it, creating a chain
Accreted terrane
1) Fragment of crustal material added to a tectonic plate, found at convergent plate boundaries.
2) explains why plate can have very different sections w. diff geologic features
Volcanic Distribution
1) found in areas of convergence
2) Ring of Fire (andesite line)
3) considered active if erupted once within historical times + likely to erupt again
benefits of volcanoes
1) most of water on earth today released as water vapor during volcanic eruptions
2) magma contains phosphorus, K, Ca, Mg
4 types of volcanoes
Shield, composite/strato, cinder cone, lava dome
Shield volcanoes
1) broad + gently sloping mountain, much broader than tall
2) made of layers of solidified lava flows
3) basaltic magma + fluid lava
Composite volcano
1) steep sided symmetrical cone
2) made of layers of lava, pyroclastics (ash/cinder), hardened volcanic mudflow
3) explosive + effusive eruptions
4) more felsic + viscous –> makes explosive
Lava Dome (Plug Dome)
1) small, irregular shape
2) made of solidified lava that was thick/viscous when molten
3) magma high in silica, explosive eruptions
Cinder Cone
1) small, steep-sided cone
2) loose pyroclastics (ash/cinder)
3) baslatic magma, short life span
4) extremely explosive
Caldera
immense basin-shaped depression (circular) with diameter much larger than volcano vent forms post eruption
ex: crater lake
Volcanic Hazards
1) Volcanic gases = sudden release of carbon dioxide + sulfur dioxide dangerous –> lead to acid rain + reduce insolation
2) lava flows –> not that dangerous BUT lava flows from intermediate/high silica magma dangerous because explosive
3) eruption column - large fragments of rock - called volcanic bombs - drop to ground + lots of ash falls
4) pyroclastic flow - high speed avalanche of searing hot gases, ash, rock
5) volcanic mudflows - caused when hot ash mixes with water/melting snow –> produces slurry of mud/boulders
Types of folding
1) Anticline
2) Syncline
Anticline
1) symmetrical upfold - creates mountains
2) Sad face parabolas
syncline
1) symmetrical downfold - creates valleys
2) Happy face parabola
Two types of tectonism
1) folding = crustal rocks become deformed because of lateral compression
2) faulting = rock structure is broken + one is forcibly displaced by other
Types of faults
1) Normal faults
2) reverse fault
3) thrust faults
4) strike-slip
Earthquake
1) vibration in Earth produced by shock waves caused from sudden displacement along fault
Earthquake dangers
1) Ground shaking –> liquefaction + breaking of buildings
2) landslides
3) tsunami = if underwater earthquake
Hanging wall vs footwall
1) Hanging wall = plate that is moving (on right)
2) footwall = plate the stays still (on left)
Normal Fault
1) Normal faults = (GOING APART) tension stresses (pulling apart) –> produces steeply inclined fault zone
Reverse Fault
1) reverse fault = (COMING TOGETHER) compression stresses (pushing together), one block slides UP incline
2) hanging wall pushed up
Thrust Fault (don’t need to know)
1) thrust faults = Earth’s crust where one piece of rock is pushed up and over another at shallow angle (less than 30 degrees)
Strike Slip Fault
1) strike-slip = lateral movement
